Single diffusion break (SDB) devices are becoming more desirable due to their improved performance capabilities. However, the present performance of such devices is affected by the resulting shape of the fin structure. Prior art processes typically include a fin reveal process that includes either a chemical oxide removal (COR) only step, or a combination of etching step and COR step. In the past, utilization of a COR only fin reveal process generally resulted in a desired rectangular fin profile, but this process removes too much of the STI oxide subjecting SDB devices to increased failure. In response, a two-step fin reveal process was utilized including both etching (e.g., radial line slot antenna (RLSA)) and COR. This combination process reduced the amount of STI oxide loss, however, the fin profile became more rounded at the top. This is undesirable as the round shape impacts contact resistance, device drive current and leakage current.
In addition to the foregoing issues of the prior art SDB FinFET device(s), when both SDB FinFET devices and double diffusion break (DDB) FinFET devices are fabricated on the same chip, it is desirable to match closely the Fin heights of the two types of devices. When utilizing an anisotropic etching process (or at least partially anisotropic process) for the Fin reveal process, including a two-step process such as etching and chemical oxide removal (COR), this results in a relatively wide recess in the silicon (and the Fin is recessed at the edges), a taller raised STI region, and shorter Fin height (silicon loss from top of fin, e.g., on order of 10 nm) and rounded Fin top.
The wider silicon recess and raised STI height degrade the aspect ratio (AR) in the SDB structure. In addition, the recessed edges of the Fin structure may result in big facets in the source/drain (S/D) region, thereby causing a weaker junction and contact landing problems. Having a short Fin height leads to weaker device performance, and may cause problems when seeking to match Fin heights between SDB structures and DDB structures.
Accordingly, there is a need for a new fin reveal process and new trench isolation structure (and methods of manufacture/fabrication) that maintain a relatively rectangular fin profile while removing less STI oxide. This achieves smaller silicon recess widths, shorter raised STI heights, increased Fin heights and/or flatter and more rectangular Fin profile tops, thereby resulting in improved device performance.